#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main()
{
	int i,n;
	int arr[20];
	arr[0] = 1;
	arr[1] = 1;
	scanf("%d", &n);
	for (i = 2; i < n; i++)
	{
		arr[i] = arr[i - 1] + arr[i - 2];
	}
	printf("%d", arr[n-1]);
	return 0;
}